1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to the image forming apparatus in which a start up time of a fixing device is shortened.
2. Discussion of the Background
An electrophotographic or ink jet image forming apparatus generally fixes a developer onto a transfer sheet by heating the developer, such as toner or ink, by using a fixing device. In the electrophotographic image forming apparatus, a heater such as a heat roll is generally used as the fixing device. Various studies have been made to stably supply the fixing device with power.
Japanese Patent Laid-Open Publication No. 8-339134 discloses an image forming apparatus having a toner image forming device that forms a toner image on a transfer sheet, a fixing device that fixes the toner image onto the transfer sheet by an electromagnetic induction heating, a temperature controller that controls a temperature of the fixing device, and at least two protectors that stop energization of the fixing device when the fixing device reaches to a temperature equal to or out of a predetermined temperature range. Thus, the image forming apparatus includes two devices (i.e., control systems) that control the temperature of the fixing device to increase reliability of the fixing device.
Japanese Patent Laid-Open Publication No. 9-197856 discloses an induction heating fixing device that includes a heated member formed of a conductive member, a coil to inductively heat the heated member, a inverter circuit to supply the coil with a high frequency, a thermistor that detects a temperature of the heated member, an output control circuit (which is electrically insulated from the inverter circuit) to control the inverter circuit based on a temperature detected by the thermistor such that the temperature of the heated member is maintained within a predetermined range, and an insulating interface that transmits a control signal input from the output control circuit to the inverter circuit while electrically insulating the control signal. Thus, the induction heating fixing device is configured to control a temperature with a low temperature ripple by electrically insulating a first circuit from a second circuit.
In a conventional image forming apparatus, because a temperature is detected with single sensor, an abnormal temperature condition occurs. Moreover, in recent years, a demand for energy savings is increasing in an image forming apparatus. Thus, attempts have been made to save energy. For example, energization of a fixing device is cut off in a standby state, or the fixing device is maintained at a temperature lower than a fixing temperature in the standby state. The present inventors have recognized that in such an image forming apparatus having an energy saving function, a quick start up is required when an image forming operation is performed. However, no technology for shortening the start up time is discussed in the above-described Japanese Patent Laid-Open Publications.
The present invention has been made in view of the above-mentioned and other problems, and addresses the above-discussed and other problems.
The present invention advantageously provides a novel image forming apparatus in which a start up time is shortened, while supplying a fixing device with power from an auxiliary power supply source when starting up the fixing device.
According to an example of the present invention, an image forming apparatus includes a fixing section configured to fix a developer transferred on a transfer sheet onto the transfer sheet by heating the transfer sheet, an energy saving power supply section configured to be supplied with power when a power switch is turned on, an energy saving control device configured to be activated by the power supplied from the energy saving power supply section, a main power supply source configured to be controlled by an on and off operation of an output by the energy saving control device, a main body control device configured to be activated by the power supplied by the main power supply source, an energy saving control release device configured to generate an energy saving control release signal so as to input the signal to the energy saving control device, and a fixing control section configured to control a temperature of the fixing section. The image forming apparatus also includes a switching device configured to start and stop supplying the power to the fixing section, and an on and off device configured to start and stop supplying the power to the fixing control section in response to the switching device. The energy saving power supply section includes an auxiliary power supply source that supplies the fixing control section with the power through the on and off device.